How to add CSS Transition when open menu?

Question

I'm still beginner to programming and I want to create a beautiful transition effect when I open the dropdowm of the menu.

In the way it is done now, the menu appears instantly, without any kind of transition. In menus that do not have a dropdown, I managed to create a transition effect. But I don't know how to create this transition effect for the dropdown.

Can you tell me how do I create a transition effect for when I open the dropdown menu?

I put my code into codesandbox.io

import "./styles.scss";
import { NavLink } from "react-router-dom";

export default function App() {
  const onCompany = (e) => {
    e.preventDefault();
  };

  return (
    <div className="App">
      <div className="menu-content">
        <ul className="menu-links">
          <li>
            <NavLink to="/services">Services</NavLink>
          </li>
          <li>
            <NavLink to="/cases">Cases</NavLink>
          </li>
          <li className="dropdown">
            <a href="/#" onClick={onCompany}>
              Our company
            </a>
            <div className="dropdown-content">
              <NavLink to="/about">About</NavLink>
              <NavLink to="/careers">Carrers</NavLink>
              <NavLink to="/articles">Articles</NavLink>
            </div>
          </li>
        </ul>
      </div>
    </div>
  );
}

.menu-content {
  display: flex;
  height: 104px;
  justify-content: center; 
}

.menu-links {
  display: flex;
  justify-content: space-between;
  list-style-type: none;
  text-decoration: none;
  margin: 0;
  height: 100%;
  width: 45%;
}

li {
  display: flex;
  flex-direction: column;
  justify-content: center;
  font-family: Alliance2;
  transition: transform 250ms ease-in-out;

  &:nth-child(-n + 2) {
    &:after {
      display: block;
      content: "";
      border-bottom: solid 3px #000;
      transform: scaleX(0);
      transition: transform 250ms ease-in-out;
    }
    &:hover:after {
      transform: scaleX(1);
    }
  }

  a {
    align-items: center;
    color: #000;
    display: flex;
    font-size: 22px;
    font-weight: 600;
    padding: 5px;
    height: 100%;
    text-decoration: none;
  }

  &.dropdown {
    .dropdown-content {
      top: 100%;
    }
  }
}

.dropdown-content {
  display: none;
  min-width: 160px;
  position: absolute;
  text-transform: uppercase;
  background-color: grey;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  top: 104px !important;

  a {
    display: block;
    font-size: 14px;
    font-weight: 600;
    color: #000;
    padding: 12px 16px;
    text-align: center;

    &:hover {
      color: #fff;
    }
  }
}

.dropdown:hover .dropdown-content {
  display: block;
}

Thank you in advance for any help.

Answer 1

Add to your styles.scss

.dropdown-content {
  opacity: 0;
  transition: opacity 1s ease;
}

.dropdown:hover .dropdown-content {
  opacity: 1;
}